Worrell V E, Nagle D P
Department of Botany and Microbiology, University of Oklahoma, Norman 73019.
J Bacteriol. 1990 Jun;172(6):3328-34. doi: 10.1128/jb.172.6.3328-3334.1990.
The enzymes involved in the purine interconversion pathway of wild-type and purine analog-resistant strains of Methanobacterium thermoautotrophicum Marburg were assayed by radiometric and spectrophotometric methods. Wild-type cells incorporated labeled adenine, guanine, and hypoxanthine, whereas mutant strains varied in their ability to incorporate these bases. Adenine, guanine, hypoxanthine, and xanthine were activated by phosphoribosyltransferase activities present in wild-type cell extracts. Some mutant strains simultaneously lost the ability to convert both guanine and hypoxanthine to the respective nucleotide, suggesting that the same enzyme activates both bases. Adenosine, guanosine, and inosine phosphorylase activities were detected for the conversion of base to nucleoside. Adenine deaminase activity was detected at low levels. Guanine deaminase activity was not detected. Nucleoside kinase activities for the conversion of adenosine, guanosine, and inosine to the respective nucleotides were detected by a new assay. The nucleotide-interconverting enzymes AMP deaminase, succinyl-AMP synthetase, succinyl-AMP lyase, IMP dehydrogenase, and GMP synthetase were present in extracts; GMP reductase was not detected. The results indicate that this autotrophic methanogen has a complex system for the utilization of exogenous purines.
采用放射性测定法和分光光度测定法对嗜热自养甲烷杆菌马尔堡野生型菌株和嘌呤类似物抗性菌株嘌呤相互转化途径中涉及的酶进行了测定。野生型细胞能掺入标记的腺嘌呤、鸟嘌呤和次黄嘌呤，而突变菌株在掺入这些碱基的能力上有所不同。腺嘌呤、鸟嘌呤、次黄嘌呤和黄嘌呤可被野生型细胞提取物中的磷酸核糖基转移酶活性激活。一些突变菌株同时丧失了将鸟嘌呤和次黄嘌呤转化为各自核苷酸的能力，这表明同一种酶可激活这两种碱基。检测到腺苷、鸟苷和肌苷磷酸化酶活性可将碱基转化为核苷。检测到低水平的腺嘌呤脱氨酶活性。未检测到鸟嘌呤脱氨酶活性。通过一种新的测定方法检测到了将腺苷、鸟苷和肌苷转化为各自核苷酸的核苷激酶活性。提取物中存在核苷酸相互转化酶，即AMP脱氨酶、琥珀酰-AMP合成酶、琥珀酰-AMP裂解酶、IMP脱氢酶和GMP合成酶；未检测到GMP还原酶。结果表明，这种自养型产甲烷菌具有一个利用外源嘌呤的复杂系统。
